As the development technique and demand for a mobile device have increased, the demand for a secondary battery as an energy source has rapidly increased, and among the secondary batteries, a lithium secondary battery having high energy density and voltage is commercialized and widely used.
In particular, a lithium secondary battery for an electric vehicle requires good long life characteristics and storage characteristics at high temperature due to the characteristics of the place where it is used, and in order to implement this, artificial graphite is widely used.
However, though the artificial graphite shows excellent life characteristics and high temperature storage characteristics as compared with natural graphite, there are problems of a high manufacture cost, a low capacity, and reduced output characteristics due to increased battery resistance.
In order to improve the resistance characteristics of the artificial graphite as such, carbon is coated on the surface of the artificial graphite, or conductive materials having excellent conductivity is added thereto to decrease the resistance of an anode, however, a trade-off phenomenon to reduce the reliability and stability of the battery is shown, which is difficult to be improved, even in the case of changing a solvent composition of an electrolyte solution and an additive composition.
Accordingly, there is currently a need to develop a lithium secondary battery having excellent life characteristics and high temperature storage characteristics which are the merits of artificial graphite, and also having improved output characteristics.
As a similar related document to this, Korean Patent Laid-Open Publication No. 10-2015-0030705 (Mar. 20, 2015) has been published.